The use of hollow bars to channel and distribute a gaseous fluid or liquid has already become known, since it was proposed by the same applicant. Each bar for this use is advantageously composed of an extruded section made of aluminum, of quadrilateral section, having a central longitudinal hole and, on the sides, channel-like grooves, which are also longitudinal and open towards the outside. Such a bar is connected modularly with other bars of the same type, in a line or at an angle, by means of tubular joints, essentially of round section, and with the use of removable connecting plates or brackets.
Each tubular joint, which may be straight, at an angle, T-shaped or cross-shaped, has one or more branches, which are inserted into the hole of the bars to be connected and which have at least one packing for a fluid seal in the fit between the joint and the inner surface of the hole.
The connecting plates or brackets are then fixed by means of screws to the slide blocks inserted into the channel-like grooves of the bars to be joined and are used to keep the bars joined to one another and to the joint.
However, such a way of connecting the duct bars is not without drawbacks. Each joint, though having at least one seal packing, which is inserted by force into the hole of a bar, is not effectively anchored to the bar itself, but can be moved in relation to this bar, either towards the outside, or towards the inside, because of the force of the fluid distributed. Thus, the safety of the system is diminished, especially at the level of the end joints, when they are blind and used as plugs for closing the hole of a bar.
On the other hand, the connecting plates or brackets join the ends of the bars without directly engaging the joints, and if they are shaped to be engaged with these joints, the assembly becomes complicated as the bracket and joint must be mounted together.